Light-emitting panel for illuminating or displaying images provided with a composite transparent upper electrode

Abstract

At least one of the upper electrodes of the panel is common to a plurality of diodes and comprises a first conducting layer and a second conducting layer, with a transparent insulating buffer layer interposed between these two conducting layers and which is pierced by windows that provide direct contact zones for direct contact between these two conducting layers of this common electrode, these contact zones being separate from the active zones of the diodes. Thanks to the direct contact zones between the two conducting layers, the upper electrode ensures good distribution of the current, while the intermediate buffer layer is insulating.

1. An illuminating or image-display panel, comprising an array of organic light-emitting diodes supported by a substrate, at least one array of lower electrodes in contact with the substrate and an array of upper electrodes,
 in which each diode comprises an organic electroluminescent layer which is interposed between one of said lower electrodes and one of said upper electrodes, wherein said upper electrodes are transparent to the light emitted by this diode, 
 in which at least one of said upper electrodes is common to a plurality of diodes and comprises a first conducting layer in contact with the organic electroluminescent layer, a second conducting layer overlaying the first conducting layer and a transparent intermediate buffer layer interposed between the first and second conducting layers, 
 wherein, for each of said at least one upper electrode common to a plurality of diodes, said intermediate buffer layer is pierced by windows that provide direct contact surfaces for direct contact between the first and second conducting layers of this at least one upper common electrode, 
 wherein the direct contact surfaces of said first conducting layer corresponds to an opposite surface of said first conducting layer that is not in contact with the organic electroluminescent layer. 
 
     
     
       2. The panel as claimed in  claim 1 , wherein, for each said upper electrode, the surface conductivity of said intermediate buffer layer is less than one tenth of the surface conductivity of the second conducting layer of said upper electrode. 
     
     
       3. The panel as claimed in  claim 1 , wherein, for each said common upper electrode, the surface conductivity of said intermediate buffer layer is less than the surface conductivity of said first conducting layer of said upper electrode. 
     
     
       4. The panel as claimed in  claim 1 , wherein, for each said common upper electrode, the material of said intermediate buffer layer is chosen from the group formed by silicon oxide, silicon nitride, silicon oxynitride and tantalum oxide. 
     
     
       5. The panel as claimed in  claim 1 , wherein, for each said common upper electrode, the material of said second conducting layer is oxide-based. 
     
     
       6. The panel as claimed in  claim 5 , wherein said oxide is chosen from the group formed by a mixed indium tin oxide (ITO) and a mixed indium zinc oxide (IZO). 
     
     
       7. The panel as claimed in  claim 5 , wherein the thickness of said second conducting layer is equal to or greater than 100 nm. 
     
     
       8. The panel as claimed in  claim 1 , wherein, for each said common upper electrode, the material of said first conducting layer is metallic. 
     
     
       9. The panel as claimed in  claim 8 , wherein the thickness of said first conducting layer is greater than 1 nm but does not exceed 20 nm. 
     
     
       10. The panel as claimed in  claim 1 , wherein, for each said common upper electrode, the thickness of said second conducting layer is greater than the thickness of said first conducting layer. 
     
     
       11. The panel as claimed in  claim 1 , wherein, for each said common upper electrode, the surface conductivity of said second conducting layer is greater than the surface conductivity of said first conducting layer.